07 crf230f

RayoVac

I have always worn a long sleeve undershirt for MX. Yes... its hotter then crap. I only do it for one reason... self preservation. Call it a rash preventer.. I seem to crash often enough that the little bit of extra protection to keep me from getting all scraped up... seems to be worth the heat endured.

YZrider2112

Memnok

+1 with the Under Armor shirt. I have one for the Summer and a long sleeve version for the Winter.

+2 for the Under Armor. I wear a cheaper Nike version under a compression suit. I was worried that the long sleeves would be too hot, but any air passing by feels like a air conditioning. I don't know how it works, but it does. Of course it's a dry heat in California, so maybe it wouldn't work so well in the south.

trailmeisterjoe

obviously temperature is the key factor here. we ride year 'round out here and pretty soon it gets cool enough for another layer. NEVER a cotton t-shirt as it gets wet and holds cold to your body. under armor type wicks away moisture and dries fast. it beats adding a light jacket if you dont need to. same with underarmor leggins' too as it cools down.

tal06

i wear skins. not sure if that counts as a shirt but i cant tell the difference temp wize between wearing them and not wearing them even in 40C heat. plus when i take my jersey off i dont have to sit around topless like a dbag or stink up a fresh shirt.

edit: do you guys get fit chicks jogging in skins over there without realising that it's actually underwear? its freaking awesome. god bless the skins inventors.